1. Field of the Invention
The present invention relates to a rechargeable battery. More particularly, the present invention relates to a rechargeable battery with an improved sealing structure of an electrolyte injection opening.
2. Description of the Related Art
Distinct from a primary battery, a secondary (rechargeable) battery can be repeatedly charged and discharged. Recently, researchers are developing high-power rechargeable batteries using non-aqueous electrolyte which has a high energy density.
Low-capacity batteries having a single battery pack are used as a power source for various portable electronic devices such as mobile phones and laptop computers. High-capacity rechargeable batteries formed using tens of battery cells connected to each other may be used as a power source for driving a motor in a device requiring high power, such as an electric vehicle.
A rechargeable battery includes an electrode assembly of a shape such as a jelly-roll configuration having a positive electrode and a negative electrode with a separator interposed between them, a case having a space for housing the electrode assembly, a cap plate combined with the case to seal the case, and a positive terminal and a negative terminal protruding toward the cap plate and electrically connected to the positive electrode and the negative electrode, respectively.
Rechargeable batteries are manufactured in diverse shapes, such as cylindrical shapes and prismatic shapes which are selected and used according to device requirements for a rechargeable battery.
The cap plate is welded onto the case to seal the case and an electrolyte injection opening is formed in the cap plate through which electrolyte solution is injected into the case. To prevent the electrolyte solution from leaking out of the case, an electrolyte sealing member is mounted on the electrolyte injection opening.
In conventional rechargeable batteries, a spherical electrolyte sealing member having a diameter larger than that of the electrolyte injection opening is mounted and pressed onto the circular electrolyte injection opening and fixed onto the cap plate by laser welding.
However, when the spherical electrolyte sealing member seals the electrolyte injection opening, as used in conventional rechargeable batteries, it is difficult to securely weld the electrolyte sealing member onto the cap plate because the upper surface of the electrolyte sealing member may not form an exact circle. Thus, a laser used for welding is not well irradiated onto the junction face. Further, when the electrolyte sealing member is inserted into the electrolyte injection opening and welded thereto, a portion between the electrolyte injection opening and the electrolyte sealing member may be smeared with electrolyte solution, thus deteriorating the weld. Poor welding may allow the electrolyte solution to leak out along the electrolyte injection opening causing a short-circuit.